Abstract: The spatial distribution of vegetation groups in river channels has an important influence on the upstream and downstream flow characteristics and the riverbed evolution of vegetation groups. In order to study the influence of different arrangements of vegetation groups on flow structures, a flume experiment is designed under the condition of the fixed bed. PVC cylinder is used to simulate two identical rigid non-submerged vegetation groups, and four groups of different distances between upstream and downstream vegetation groups are set up. By studying flow velocity and turbulence intensity distribution, the formation and development process of upstream flow adjustment length and wake are analyzed under different spaces between upstream and downstream vegetation groups, and the effect of individual vegetation on flow structures is compared. The results show that upstream vegetation groups shorten the length of downstream vegetation groups’ front adjustment zone, which has nothing to do with vegetation group spacing. With the emergence of upstream vegetation groups, the overflow velocity of downstream vegetation groups, the length of wake stabilization zone and the velocity of stabilization zone all decrease, and their sizes are related to the spacing between vegetation groups, and the smaller the spacing is, the smaller each value is. At the same time, the length of wake formation zone of downstream vegetation groups became shorter, and decreased first and then increased with the increase of spacing.The wake recovery rate of the downstream vegetation groups changed more rapidly with the emergence of the upstream vegetation. The existence of upstream vegetation groups intensified the wake turbulence of downstream vegetation groups, and the change trend was also related to the spacing of vegetation groups. Vegetation groups have both inhibiting and promoting effects on water flow, mainly depending on the intensity of turbulence in front of vegetation groups. The effects of different longitudinal spacing of vegetation groups on river flow structure were investigated, which provided a supplement for the effects of spatial distribution of vegetation groups on river flow characteristics.